The goal of the PPG (Gene Therapy for Cystic Fibrosis) is to create gene transfer vectors that will efficiently transduce cells of the lung. Major but not exclusive therapeutic targets are the epithelia of the large and small airways, which are the sites of cystic fibrosis lung disease. The major hypothesis tested in the PPG are (1) new vectors are needed, including higher capacity, better expressing AAV vectors; high titer, safe lentiviral vectors; and adenoviral vectors specifically targeted to airway epithelial receptors; and (2) that a rate-limiting variable for gene transfer efficiency in the lung is at the site of initial vector-cell interaction, including both binding and entry across the plasma membrane. Three projects and four Cores are proposed. Project 1 (Parvovirus Vectors for Airway Delivery, R.J. Samulski, P.I) proposes to design and produce new AAV vectors that increase the vector packaging size, augment the efficiency of vector entry, and increase the efficiency of expression (conversion from single strand to double strand DNA templates) using chimeric virion capsids, targeting ligands and modified viral terminal repeats. Project II (Equine Lentiviral Vector for Gene Delivery, J.C. Olsen, P.I.) proposes to develop high titer, efficiently expressing, and safe equine lentiviral vectors. Project III (Cell Biology of Airway Epithelial Gene Transfer, Raymond Pickles/R.C. Boucher and M. Peeples, PI) proposes to define the barriers and targets in the apical domain of airway epithelia, modify the barriers using either oxidant injury or more specific modulators of the tight junctions, and finally, modify vectors to target a class of receptors on the apical membrane that exhibit cellular internalization in response to agonist addition. The projects are supported by an Administrative Core (core A), a Cell Culture Core (Core B), a Vector Core (Core C) and an Imaging Core (Core D). The PPG is a highly interactive program designed to modify vectors and test their interactions with target cells in vitro and in murine models in vivo.